The present invention relates to polyvinyl chloride (hereinafter PVC) polymeric substrates and more particularly to a new anti-stat blend therefor.
The accumulation of static electricity on parts can lead to many problems. One problem is that static electricity build-up on a part causes dirt or other particulate matter to be attracted and adhere to the surface of the part. In some manufacturing environments, such dirt or other particulate matter can lead to difficulties in manufacturing, lowering of performance of certain parts, and other associated problems. Another problem associated with static electricity build-up is the danger that electrical and electronic components coming into contact with such charge build-up can become damaged thereby.
A further problem associated with static charge build-up involves safety concerns. Some manufacturing and other service areas express a high risk of a severe explosion hazard, such as, for example, in operating theaters of hospitals, in paint shops, in chemical manufacturing areas, and like environments. It will be appreciated that potential explosive environments pervade such locations, including, for example, oxygen, volatile organic solvents, and like material which may be susceptible to fire or explosion. The prevention of static electricity build-up on parts used in such environments is desirable.
While anti-static topical treatment of polymeric parts has been proposed, such topical treatments are subject to erosion with attendant loss of activity. Another proposal for dissipating static electricity involves the incorporation of an anti-static agent or anti-stat as an internal additive in the polymer during its processing. While some anti-stats have enjoyed acceptance in the marketplace, the particular problem in developing acceptable anti-stats for PVC polymers has arisen because conventional anti-stats are formulated from ethoxylated amines and quaternary ammonium compounds. Such nitrogen-containing materials, however, tend to adversely affect PVC and, thus, their use in PVC is not recommended. Other PVC anti-stats in the marketplace include glycerol mono-oleate, glycerol mono-stearate, polyoxyethylene sorbitan mono-laurate, diethylene glycol laurate, and polyethylene glycol mono-stearate. Several of these materials are disclosed in U.S. Pat. No. 3,145,187.
Another problem facing anti-stats, including internal additives, involves the degree of plasticization of the PVC part. Some conventional PVC anti-stats function quite effectively at moderate to high plasticizer levels. However, when the plasticizer level is diminished to make a semi-rigid or rigid part, the anti-stat fails in its effectiveness. Apparently, the combination of plasticizer and anti-stat is necessary in order for the requisite charge dissipation to be realized. Thus, an anti-stat effective in flexible, semi-rigid, and rigid PVC material is desired by the art.